This invention relates to a process of reforming cyclic alkyleneamines to amine-extended cyclic alkyleneamines. Examples of amine-extended cyclic alkyleneamines include bis(piperazinyl)alkanes, bis(piperidinyl)alkanes, (aminoalkyl)bis(piperazinyl) alkanes, and higher homologues of these compounds, such as tris(piperazinyl)-alkanes and (aminoalkyl)tris(piperazinyl)alkanes.
Amine-extended cyclic alkyleneamines are useful as dispersants, surfactants, chelants, catalysts, curing agents, extenders in polyurethanes, and as starting materials in the preparation of pesticides.
It is known that bis(piperazinyl)alkanes and bis(piperidinyl)alkanes can be prepared by the reaction of an alkyl dihalide with piperazine or piperidine, respectively. The reaction yields the corresponding hydrohalide salts which must be neutralized with base in order to recover the valuable bis(piperazinyl)alkane and bis(piperidinyl)alkane products. Disadvantageously, the neutralization produces a waste stream of metal salt which must be removed.
Other organic syntheses of bis(piperazinyl)alkanes and bis(piperidinyl)alkanes are known. For example, U.S. Pat. No. 2,716,134 discloses the preparation of N,N'-bis(piperidinyl)pentane comprising reacting piperidine with 1,5-di(methanesulfoxy)pentane. Disadvantageously, the sulfoxy-containing reactant is difficult to obtain, and the products do not include any higher homologues of N,N'-bis(piperidinyl)pentane.
Direct catalytic methods of preparing amine-extended cyclic alkyleneamines are also known. For example, U.S. Pat. No. 4,552,961 discloses a process for the preparation of polyalkylene polypiperazines comprising reacting piperazine or aminoethylpiperazine with alkanolamines or alkylene glycols in the presence of a phosphorus amide catalyst. Disadvantageously, this catalyst is homogeneous and must be separated from the product stream. In addition, the process generates water as a by-product which must be separated from the polypiperazine products.
Typically, direct catalytic methods involving cyclic alkyleneamines tend to yield undesirable products from internal cyclization, cracking, and dehydrogenation. For example, U.S. Pat. No. 3,956,329 discloses contacting N-(2-aminoethyl)piperazine with a catalyst comprising an aluminosilicate zeolite of the formula: EQU a(M.sub.2 /.sub.n O).(Al.sub.2 O.sub.3).m(SiO.sub.2)
wherein M represents a cation selected from alkali metals, alkaline earth metals, zinc group elements, and hydrogen and ammonium cations; "n" represents the valence of the cation, "a" represents 1.0.+-.0.5 regardless of the type and number of the cation, and "m" represents the numbers 2 to 12. Disadvantageously, this process produces large quantities of internal cyclization and cracking products, such as triethylenediamine and piperazine.
U.S. Pat. No. 2,474,781 discloses contacting piperazine in the vapor phase at an elevated temperature with a catalyst comprising a Group VB or VIB oxide, such as vanadium oxide or tungsten oxide, supported on alumina. Disadvantageously, the products include large quantities of dehydrogenation products, such as pyrazine.
Similarly, the vapor phase deamination of N-(2-aminoethyl)piperazine at 400.degree. C. over a kaolin catalyst is reported by A. A. Anderson et al. in Doklady Akademii Nauk SSSR, 169 (6), (1966), 1332-1334, to yield cracking products, such as ethylenediamine and piperazine; dehydrogenation products, such as pyrazine; and internal cyclization products, such as triethylenediamine.
Among the different processes reported in the prior art, none appears to be selective to amine-extended cyclic alkyleneamines and also suitable for commercial application. It would be desirable to find an inexpensive catalyst which is capable of reforming cyclic alkyleneamines directly to amine-extended cyclic alkyleneamines. It would be more desirable if such a process produced high yields of amine-extended cyclic alkyleneamines and simultaneously low yields of cracking products, dehydrogenation products, and internal cyclization products. It would be even more desirable if the catalyst for such a process was insoluble in amines and water, so as to avoid catalyst losses and separation problems.